Add instructions for adding and editing translations using i18n (#1120)

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Remove ignore_keys

website/docs/add_edit_translations.md

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+## Adding new locales to i18n
+
+This guide will help you add a new locale to the `i18n` setup.
+
+### Prerequisites
+
+- An up-to-date branch with the `main` branch.
+- Familiarity with `i18n`, `react-i18next`, and `next-i18next` libraries is beneficial.
+
+### Adding a new language
+
+1. Determine the language and country codes using `ISO 639-1`. For example, `en` for English.
+1. Create a new directory within the `public/locales` directory using the language and country codes as the name, for
+   example `en`.
+1. Copy all the files from the `en` directory into the newly created directory.
+1. Edit the copied the text in the copied files with the desired language.
+1. Add the new language to the list in `next-i18next.config.js` if it does not already exist.
+1. Follow the instructions in [Website README](<[README.md](../../../website/README.md)>) to run and test the new
+   language by changing the active locale in the application and verifying that all translated keys are properly
+   displayed.
+1. Commit your changes and open a pull request against the `main` branch for review.
+
+### Editing existing translation files
+
+When editing existing translations, follow these rules:
+
+1. English translations are required, and other locales fall back to them.
+1. Keep translation keys in alphabetical order.
+1. Add all translations for higher-level components (e.g. `Layout.ts`) in `common.json` to prevent hydration issues.
+1. Add reused translation keys in `common.json`.
+1. Split translation files into separate files by feature or route.
+
+### Finding missing translations
+
+A script can be used to find missing and potentially untranslated locale files. Run the script from the root dir using
+`python scripts/frontend-development/find-missing-locales.py`.
+
+If you have any questions or need further assistance, please reach out.